Some electric powered automotive vehicles comprise electrical power systems having a plurality of battery cells arranged to provide a high voltage electricity supply. In some such vehicles, battery cells are grouped together into battery modules, and a plurality of battery modules are connected together to form a battery stack. For reasons including, among other things, optimizing battery performance and ensuring batteries operate safely, it is desirable to monitor operational characteristics of individual battery cells (e.g., voltage, charge, current, temperature, etc.) within a battery stack, and to control the operation of individual battery cells (e.g., charging, discharging, load, etc.).
In some electric powered automotive vehicles, control of individual battery cells is coordinated (e.g., by a central controller and/or cooperation among different controllers). Such coordination requires communication between apparatus which monitor characteristics of and/or control one or more particular battery cells (e.g., groups of battery cells, such as the cells of a particular battery module) and one or both of other such apparatus and a central controller. Such communication may be facilitated by a network that interconnects monitoring/control apparatus and/or a central controller.
Several challenges are associated with networking monitoring/control apparatus and/or a central controller in an automotive environment, including, for example:                electrical noise, heat and physical interference, and other adverse conditions characteristic of the automotive environment present multiple failure modes for wiring, wiring connections and signaling;        space limitations and the requirement that automotive systems be amenable to rapid assembly limits the complexity of wiring configurations that may reasonably be implemented; and        battery stacks may be modular and/or have different configurations among different vehicles, such the same network topology cannot be applied to all configurations.        
There is accordingly a desire for improved apparatus and methods that enable communications between and/or among battery cells monitoring/control apparatus and/or central controllers.
A ground fault in the power system of an electric powered automotive vehicle is undesirable, for example because it may pose a shock hazard and/or drain the electrical power supply of the vehicle. Accordingly, it is desirable that the presence of a ground fault be detected, in order that it can be remedied or other corrective action taken. It is further desirable that a ground fault be characterized, for example by impedance, in order that the cause of the ground fault may more quickly be determined. There is accordingly a desire for improved apparatus and methods for detecting and characterizing ground faults in the power systems of electric powered automotive vehicles.
Patent literature describing technology relating to the general field of this invention includes:                U.S. Pat. No. 7,755,326;        U.S. Pat. No. 6,020,717;        U.S. Pat. No. 7,199,489;        U.S. Pat. No. 6,078,165;        U.S. Pat. No. 5,701,068;        U.S. Pat. No. 5,710,501;        U.S. Pat. No. 6,094,031;        U.S. Pat. No. 7,405,579;        U.S. Pat. No. 7,511,457;        U.S. Pat. No. 7,471,065;        U.S. Pat. No. 3,740,652;        U.S. Pat. No. 6,906,525; and        US Patent Application Publication No. 2010/0052692.        
The inventors have determined a need for improved battery monitoring systems. The inventors have further determined a need for battery monitoring systems which provide robust safety protection and reduced manufacturing costs.